US2660126A - Emergency dynamic braking system - Google Patents

Description

3 Sheets-Sheet- 1 Filed Dec. 50, .1949

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INVENTORS Maxwell D. Brone and Allen McLonohon. BY

ATTORNEY Nov. 24, 1953 D, B ANE Em 2,660,126

EMERGENCY DYNAMIC BRAKING SYSTEM Filed Dec. 30, 1949 3 Sheets-Sheet 2 m WITNESSES: o N

INVENTORS 471f' Mox-wellD.Brune and A Bwcmnqhun.

ATTORNEY Nov. 24, 1953 Filed Dec. 30, 1949 M. D. BRANE ETAL 3 Sheets-Sheet 3 3 Nbrmol 2 Run-Brokin Figs 2 0 Sequence 8 "ii 0 l R2 R4|R R R l0 12 BI B2 3 o o o g 4 0 0 0 O "a: 5 o o o o 0,.

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ATTORNEY Patented Nov. 24, 1953 UNITED STATES FAYTENT OFFICE EMERGENCY DYNAMIC BRAKING SYSTEM Maxwell .D. Brane, 'Wexforcl, and Allen McLa'nahan, Pittsburgh, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a, corporation-oi Pennsylvania Application December 30, 1949, SefialNo. 135;978

'6 Claims. 1

Our invention relates, generally, to dynamic braking systems and, more particularly, to systems for establishing dynamic braking under emergency conditions.

In the interest or" safety there is need for protective features to be installed on electric vehicles, such as mining locomotives, to limit locomotive speed to a safe value in order to decrease the number of derailments and wrecks.

An object of our invention is to provide for automatically taking the control of a locomotive away from the operator and applying dynamic braking under predetermined conditions.

Another object of our invention is to provide forautomatically limiting the speed of a locomo- Y tive by applying dynamic braking under the control of a current limit relay when it is operating on certain sections of track as, for example down gradesor around-curves.

A further object of our invention, is to provide for automatically limiting the maximum speed of a locomotive by applying dynamic-braking under the control of a current limit relay "which prevents locking the wheels by the dynamic brake under usual track conditions.

Still another object of our invention "is to require the operator to perform-certain definite operations before power can be reapplied to a locomotiveafter dynamic braking has beenautoinatically applied.

A more general object of our invention is to provide an emergency dynamic braking system which shall be sim le and efiicient in operation and which may be economically manufactured andinstalled.

A still further object of our invention is 'to provide an emergency dynamic braking'system which may be readily installed on existing locomotives.

Gther objects of our invention will be "exlimit relay to slowthe locomotive down to a safe 6 speed. The operator must return the master controller handle to the off position before power can be reapplied to themotors.

For a better understanding of the nature and objects of our invention, reference may be had under predetermined "Switch 1 eration of the control apparatus in Fig. 1 under preset braking conditions;

Fig. 5 is a chart showing the sequence of operation-cl the control apparatus in Fig. 2 when the locomotive exceeds a predetermined speed, and

Fig. 6 is a diagrammatic view illustrating the method of presetting the control apparatus when the locomotive'is descending a grade.

Referring to the drawings-and particularly to Figure l, the system shown therein comprises traction motors M1 and M2 which may be of a type suitable for "propelling an electric locomotive (notshown). The motor Ml has an armatture winding [3 and a series field winding 14. Likewise,'the motor M2 has an armature winding l5 and a seriesfield winding [6.

The power for operating the motors M! and M2 may be supplied througha power conductor ll which is connected to a current collecting device 58 which, in turn, engages a trolley conductor [9. The conductor [9 maybe energized from any suitable source, such as a power generating station (notshown) A resistor Ris provided for limiting the motor current during both acceleration and dynamic braking ofthe locomotive. One terminal of the resistor R is connected to the power conductor ll through one .set of contact members of 4a The other terminal of the resistor R is connected to the motors MI and M2 through another set of contact membersof the-switch l. The resistor B may be shunted from the motor circuit step-by-step by means'oi resistor shunting switches R2, R4, R6, R7, R8, RH) :and RH in a mannerwell known in the'art.

A dynamic braking :circuit forthe astors in! and M2 may be establish-ed through switches'Bl and B2. The dynamic braking circuit is of a well-known-type in which tlie'armature winding l3 of the motor M1 is connected across the field winding I6 of the motor M2 and the armature 3 winding l of the motor M2 is connected across the field winding IA of the motor MI.

The operation of the line switch I and the resistor shunting switches is controlled during acceleration by means of a master controller MC. Under normal conditions the operation of the dynamic braking switches Bi and B2 and the resistor shunting switches is controlled by the con troller MC.

A current-limit relay CL is provided for controlling the progression of the resistor shunting switches to limit the dynamic braking current to a predetermined amount. The contact members of the current-limit relay CL are so connected in the control circuit that the progression of the resistor shunting switches is stopped when the motor current exceeds the setting of the limit relay.

In order to limit the locomotive speed on grades or around curves provision is made for automatically establishing dynamic braking independently of the position of the controller MC by means of an emergency relay E and limit switches LSI and LS2 which are actuated by actuating devices 2| and 22, respectively, disposed at predetermined locations along the track over which the locomotive operates. The switch LSI may be of a type which is normally biased to its off position and is actuated to its closed position by the device 2| as the locomotive passes this device which may be located at the top of a grade.

When the locomotive passes the device 22 which may be located at the bottom of the grade, the switch LS2 is actuated from its closed position to an open position. It will be understood that the switches LSI and LS2 return to the positions shown in the drawing when released by the actuating devices 2 I and 22.

The emergency relay E, the operation of which is controlled by the switches LSI and LS2, is provided with contact members which eiiect the closing of the dynamic braking switches Bl B2 and also cause certain of the resistor shunting switches to be closed under the control of the limit relay CL to limit the speed of the locomotive while the relay E is closed, as will be subsequently described. During this time the operator of the locomotive can further reduce the speed if he so desires by operating the controller to close additional resistor shunting switches, but he can not exceed the predetermined speed.

In order to require the operator to return the controller MC to the off position before reapplying power to the motors after the operation of the emergency relay E, a no-voltage relay NV is provided. The actuating coil of the relay NV is energized by the potential of the power conductor H and the contact members of the relay are so connected in the control system that the controller MC must be returned to the of! position before the switch I can be reclosed to a p y power to the locomotive after the operation of the relay E, as will be subsequently described.

In order that the functioning of the for going apparatus may be more clearly understood, the operation of the system will now be described in more detail. Assuming that it is desired to apply power to the motors MI and M2 to accelerate the locomotive, a switch CS is closed and the con-- troller MC is actuated through the running posi tions step-by-step.

When the switch CS is closed the actuating coil of the no-voltage relay NV is energized through a circuit which extends from the power conductor I! through the switch CS, conductor 23, the coil of the relay NV, a resistor 20 and contact members El to ground. When the controller MC on position 1 the actuating coil of the switch i is energized through a circuit which. may be traced from positive through a segment 2:? on the controller MC, conductor 25, the coil oi switch l, interlock Bi 2, conductor 26, an interlock B21, conductor 21, and contact members NV! to ground.

As explained hereinbeiore the closing or the switch I connects the motors MI and M2 to the power source through the resistor R. switches R2, R4, R6, R7, R16 and Pi" be closed in sequential relation by actua controller MC through positions 2 to 3, shunting the resistor R from the motor The energizing circuit for the switch R2 traced from positive through the con ment 24, conductor 28, contact members he, ductor 29, a segment 3| on the controller IC, conductor 32 and the coil of the switch ground. The energizing circuit for ti Rd extends from the segment thro r ductor 33, the coil of the switch Rt, conduct-or an interlock R21, conductor an interlock; conductor ill, and the contact members or" the current-limit relay CL to ground. A holding circuit for the switch R4 is established throi an interlock R42 upon the closing of the SWliliill.

The switch R6 is closed when the controller MC is on position 4. The energiizng circuit for the switch RB extends from the contact segment 3| on the controller MC through conductor 42, the actuating coil of the switch R5, conductor 43, an interlock R43, conductor M, an interlock RSI, conductor 3'! and the contact members of the current-limit relay CL to ground. A holding circuit for the switch R6 is established through an interlock R62 upon the closing of the switch.

The switch R1 is closed when the controller MC is on position 5. The energizing circuit for the switch R'I extends from the conductor 29 through an interlock l I on the switch I, conduc tor 33, contact segments 39 and M on the controller MC, conductor 40, the actuating coil of the switch RT, interlocks R63 and R! i, conductor 37 and the contact members of the currentdimit relay CL to ground. A holding circuit for the switch R1 is established through an interlock R122. The switches R8, RIO and R12 are closed in a similar manner when the controller MC is actuated through positions 6 to 8.

Dynamic braking may be applied in the usual manner by returning the controller MC to the off position to open the switch I and the resistor shunting switches and then actuating the controller to one of the braking positions to close the switches BI and B2. The energizing circuit for the switch Bl may be traced from positive through a segment 45 on the controller MC, conductor 28, a segment 55, conductor ti, and the coil of the switch BI to ground. The energizing circuit for the switch B2 extends from conductor 47 through the coil of the switch to ground.

The switches R2, R4, RE, R7, and RH? may be closed in sequential relation under the control of the current-limit relay CL by actuating the controller MC through the braking positions 2 to 7. Thus, the speed of the locomotive may be controlled by the operator in the usual manner.

In order to limit the speed of the locomotive when descending a grade or going around a curve, provision is made for automatically disconnecting the motors from the power source and establishing the dynamic br'aking'circiiits for-the motors. When the locomotive assestheactuating device 2| which, as illustrated in- Figure-6,-nray be located at the top of a gradaa handle 48 on the switch LS is engaged by the device 2| to actuate the switch LSI to its closed position, thereby energizing the coil of the emergency relay E. The-circuit for the coil of the relay E may be traced from positive through the switch'LSI, conductor 5!, the switch LS2 and the coil of the relay to ground. A holding circuit for-the re lay E is established through an interlock- E3 and the switch LS2. As explained hereinbefore, the switch LS! returns to the off position when the handle 48 is disengaged from the actuating member 2 l. V

The operation of the relay E interrupts the energizing circuit for the n'o-voltage relay NV, thereby causing this relay to drop to its lowermost position which interrupts the circuit through its contact members NV! for the line switch I which opens to disconnect the motors from the power source. The opening of the contact members E2 on the relay E interrupts the energizing circuit for the resistor shunting switches.

Following the opening of the line switch I the switches Bi and B2 are closed to establish the dynamic braking circuits for the motors. The energizing circuit for the switches BI and 132 may be traced from positive through contact members Ed, conductor 28, contact members E5, conductor 52, an interlock I2 on switch l and conductor 4'! to the coils or the switches BI and 52.

Following the closing of the switch Bl the resistor shunting switch R2 is closed. The energizing circuit for the switch R2 extends from the conductor 22 through an interlock BIZ, conductor 23, contact members E6 and conductor 32 to the coil of the switch R2.

Following the closing of the switch R2 the switch B6 is closed. The energizing circuit for the switch R6 extends from the conductor 29 through contact members E1 and conductor 33 to the coil of the switch R4.- The' switch R6 is closed after Rd is closed. The energizing circuit for extends from conductor 29 through contact members E8 and conductor 42 to the coil of the switch B5.

In this manner the dynamic'braking circuits are established and the resistor shunting switches R2, R4 and R6 are closed independently of the position of the master controller MC and, therefore, independently of the operator of the locomotive. If the operator so desires, he may limit the speed of the locomotive stili further by actuating the controller MC to the braking position 5, thereby clcsingthe resistor shunting switch Hi. The energizing circuit for theswitch R"! extends from the conductor 29 through segments as and ti on the controller MC and condoctor as to the coil of the switch RT.

Following the closing of the switch R1, the switches R3 and RH] are closed in sequential relation, as indicated in the sequence chart in Figure 4. As explained hereinbefore, the operation of the resistor shunting switches during dynamic braking is under the control of the current-limit relay CL in a manner well known in the art.

When the locomotive passes the actuating device 22 which, as shown in Figure 6, is located at the bottom of the grade, a handle 49 is engaged by the device 22, thereby actuating the 6 limit switch LSZ-to its open position whichinterrupts theholding circuit for the emergency relay E, thereby causing this relay todrop to its lowermost position.

The deenergization of the relay E causes the switches BI and B2 to be opened to disconnect the dynamic braking circuits. However, power can not be reapplied to the motors until after the master-controller MC is returned to the of? position since the actuating coil of the no-voltag'e relay NV is shunted, thereby causing this relay to remain open. The shunting circuit for the coiloi the relay N'Vextends from the'conductor 23 through either contact segment 55 or contact segment 56 on the controller MC, conductor 51, and contact members NV2. This shunting cir' cuitm'ay be interrupted by actuating the controller MC to the off position after which power may be a-ppliedto the motors MI and M2 by operating the controller through the running positions in the manner hereinbefore described.

The switches LS! and LS2 are so constructed that they are not operated by the devices 2| and 22 in a direction to energize the coil of the relay E when the locomotive is ascending the grade. Thus, power is maintained on the locomotive when it is ascending the grade. If it is desired to limit the speed of the locomotive when it is going around a curve in either direction the switches LS! and LS2 may be so constructed that the dynamic braking circuits will be established when the locomotive is operating in either direction. I In this manner the speed of the locomotive may be automatically limited when it is operating over'any section of the track. The actuating devices 2| and ZZ may be located at any desired points along the track.

In the modification of. the invention shown in Figure 2, in which like parts are designated by the same reference characters as in Figure 1, dynamic braking is automatically applied whenever the locomotive exceeds a predetermined speed. The energization of the emergency relay E is automatically controlled by contact members OS! of an-overspeed device OS which is connected to the motor M2. The overspeed device OS may be operated by centrifugal force or in any other suitable manner. When the contact members 05! are closed the actuating coil of the relay E is energized through a-circuit which may be traced from positive through contact members OS 1, con ductor 58, a push button switch PB, conductor 59 and the coil of the switch E to ground. A holding circuit for the coil E- is established through the contact members Et upon the closing of these contact members.

The operation of the relay E effects the establishment of the dynamic braking circuits for the motors MI and M2 in the manner hereinbefore described. Likewise, the resistor shunting switches R2, R4 and R5 are sequentially closed by the energization of their actuating coithrough contact members El and E8 on the relayE under the control of the current-limit relay 31 in the manner hereinbefore described. In the Fig. 2 system the relay is provided with additional contact members as, Eii and Eli which cause the switches R1, R5 and Bill to be closed in sequentialrelation in a mannersimilar to 'the'closing of the switches R2, R4 and R5. in this manner the locomotive speed is reduced to a low value at which dynamic braking isnolon ereffective.

' Before-power can be reapplied to the motors the-operatormust-stop-the locomotive, get off and operate the push button PB which may be so located on the locomotive that it is impossible to operate the push button without the operator leaving his normal position. The opening of the push button switch PB interrupts the holding circuit for the relay E, thereby causing this relay to drop to its lowermost position which causes the disconnecting of the dynamic braking circuits and the opening of the resistor shunting switches.

In addition to operating the push button PB it is also necessary for the operator to return the master controller MC to the oil position to permit the closing of the no-voltage relay in the manner hereinbefore described before power can be reapplied to the motors. After the no-voltage relay is closed the controller may be actuated through the running positions to reapply power to the locomotive in the manner hereinbefore described.

From the foregoing description it is apparent that we have provided safety features which automatically limit the speed of a locomotive independently oi the operator and the normal control apparatus. The systems herein described may be readily applied to existing locomotives by the addition of a relatively small amount of apparatus.

Since numerous changes may be made in the above-described construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. In an electrically propelled vehicle, a motormeans, means for causing a variable voltage to be applicable across the terminals of the motormeans for speed-control during motoring, means for establishing a variable intensity of electric braking using said motor-means as a generator, 2. normal-operation controller-means for normally putting the motoring and electric-braking operations under the control of the vehicle-operator, a current-limit relay, an emergency switching-means having a normal position and an emergency position, emergency-switch actuatingmeans which is out of the control of the vehicleoperator for actuating said emergency switchingmeans from its normal position to its emergency position in response to some particular operating-condition of the vehicle, and means responsive to the emergency position of the emergency switching-means for taking the control away from said controller-means to the extent of discontinuing any motoring operation and automatically progressively establishing a number of steps 01 electric braking under the control of the current-limit relay, regardless of the position of the controller-means, said automatically established electric-braking steps, under emergencyswitching control, being only certain of the weaker-intensity electric-braking steps, leaving the stronger-intensity electric-braking steps under the control of the controller-means.

2. In an electrically propelled vehicle, a motormeans, means for causing a variable voltage to be applicable across the terminals of the motormeans for speed-control during motoring, means for establishing a variable intensity of electric braking using said motor-means as a generator, 2. normal-operation controller-means for normally putting the motoring and electric-braking operations under the control of the vehicle-operator, a current-limit relay, an emergency switching-means having a normal position and an emergency position, emergency-switch actuatingmeans which is out of the control of the vehicleoperator for actuating said emergency switchingmeans from its normal position to its emergency position in response to some particular operatingcondition of the vehicle, means responsive to the emergency position of the emergency switchingmeans for taking the control away from said controller-means to the extent of discontinuing any motoring operation and automatically progressively establishing a number of steps of electric braking under the control of the current-limit relay, regardless of the position of the controller-means, and means responsive to an actuation of the emergency switching-means to its emergency position for thereafter requiring that the COl'ltlO11E1-l'il8L-I1S be restored to its off-position before a resetting of the emergency switching-means will enable the controller--mear.\s to regain its normal control over the motoring and electric-braking operations.

3. The invention as defined in claim 2, in which the vehicle travels over a predetermined route, and in which a safety-means is associated with said emergency-switch actuating-means, said safety-means being adapted to cooperate with means at a predetermined point in the route of said vehicle to cause said emergency-switch actuating-means to actuate said emergency switching-means to its emergency position.

The invention as defined in claim 2, characterized by said emergency-switch actuating means operating in response to a predetermined overspeed-condition of the vehicle, and further characterized by said automatically established electric-braking steps, under emergency-switching control, including all of the elec ic-bralring steps, for automatically reducing the vehicle speed to a low value at which electric braking is no longer effective.

5. The invention as defined in claim 3, in which a second safety-means is associated with said emergency-switch actuati.ng-ineans, said second safety-means being adapted to cooperate with means at another predetermined point in the route of said vehicle to cause said emergencyswitch actuating-means to restore emergency switching means to its normal position,

6. The invention as defined in claim 4, in combination with emergency-switch resetting means, under the control of the vehicle-operator but only from some position other than the operators position at the normal-operation controllermeans, for restoring said emergency switchingmeans from its emergency position to its normal position.

MAXWELL D. BRANE. ALLEN McLANAHAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,699,748 North Jan. 22, 1929 1,947,059 Ponsonby Feb. 13, 1934 2,121,605 Mardis et a1 June 21, 1938 2,128,034 Austin et al Aug. 23, 1938 2,183,409 Schiebeler Dec, 12, 1939 2,400,998 Krapf May 28, 1946 2,484,213 Fitzgerald Oct. 11, 1949

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